I am planning a new pond build early in the New Year and would appreciate the comments of experienced and expert Koi keepers on this forum to assist me in a decision to add or to leave out a separate system aiming to enhance Koi body shape.

System to be timer operated, mid water suction line from pond with a separate pump, to create return current to the pond at different levels for 4-6 hours per day.

Top water returns from Nexus and pods via 110mm pipe will be in place to circulate water in the pond

Question 1

How would the standing of water in the pipe for 18hrs a day affect the overall water quality, short term and long term?

(I am aware that I can throttle the return in the off time and thereby keep the flow going)

Question 2

What will have the best effect on Koi growth and body shape?

1. Pond depth of 2.2 to 2.5m
2. The current exercise system of 6 hrs a day
3. Both

Total pond volume to be approximately 28000lt with 6 to 8 Koi max.